1. Field of the Invention
The present invention relates to a one-way clutch used as a part such as a torque transmission and back stop in a power transmission device for an automobile and the like, for example. More particularly, the invention relates to an improved cage for the one-way clutch.
2. Related Background Art
In general, when a one-way clutch is incorporated for use in the rotating part of an industrial machine or the like, the clutch is retained in a rotative member, an outer race or inner race, with a given dragging torque so that the function of the clutch is not affected by vibration, inertia, or the like.
If, for example, the outer race is suddenly accelerated or decelerated, the sprags are caused to slip on the track surface of the outer race due to inertia and generate friction. It is, therefore, necessary to provide a frictional force, or the dragging torque, between the outer cage and the outer race to allow them to rotate together at all times. This is required to transfer the motion of the outer race to the outer cage and assure the motion of the sprags simultaneously.
To obtain a given dragging torque as described above, the entire body of an outer cage is oval in shape including an annular flange for the one-way clutch according to the prior art. Then, the annular flange and the inner circumference of the outer race are arranged to be in contact with each other at both ends of this oval-shaped cage in the direction of its major axis in order to obtain the required dragging torque.
In an example of the prior art, the diameter on the major axis of the oval-shaped cage is made slightly greater than the inner diameter of the outer race to fix them by the application of the spring force exerted by the distortion of the entire body of the cage so that the outer cage is stationary in contact with the outer race for obtaining the dragging torque.
Nevertheless, there are problems given below in the one-way clutch which has an oval-shaped cage of a conventional type as described above. First of all, it is difficult to thin the entire body of the cage or the annular flange as much as desired due to the strength factor to be taken into account. Because of this, its rigidity is set comparatively high, leading to a greater variation of the spring force (spring capability and elastic modulus) even when the dimension slightly varies in its major axis direction.
As a result, in order to obtain a required spring capability, it is necessary to strictly control the dimensions of the oval shape, particularly in its major axis direction. It is also difficult to machine the oval-shaped cages while controlling the dimensions strictly.
Furthermore, since there is a need for such a strict control of the dimensional precision, the design flexibility is rather low which can make it difficult to obtain a spring capability that is appropriately suited for a particular purpose.